Spectroscopy, imaging and Compton-scatter polarimetry with a germanium strip detector

Germanium strip detectors combine the excellent energy resolution possible with germanium detectors with fine two-dimensional spatial resolution determined by orthogonal strip electrodes. We are testing a detector with an active volume of 5×5×1 cm³ and a total of 50 electrodes, 25 on each side with a 2 mm pitch. Potential astrophysics applications include use as a focal plane for a coded-aperture telescope in the energy range ~5-500 keV, as the focal plane of a grazing-incidence telescope in the ~5-100 keV band, or in a Compton scatter telescope. The utilization of germanium strip detectors for these applications requires proof of their performance capabilities in terms of energy and spatial resolution, and efficiencies for single and multi-pixel interactions. In this paper, we demonstrate the excellent spectroscopy and imaging performance of a 2 mm pitch strip detector, and report on the results of Monte-Carlo simulations of photopeak efficiencies for single and multi-pixel interactions. These simulations show that 2-pixel interactions are a significant fraction of the photopeak efficiency in the 80-500 keV range. We demonstrate that these interactions can be used to measure linear polarization of a normally incident beam